Electric elevator system



Jan. 12, 1932. s. B. GROSVENOR 1,840,315

ELECTRIC ELEVATOR SYSTEM Original Filed March 1, 1923 2 Sheet s-Sheet 1 .INVENTOR E55 GRAHAM B. 6/?05/[11/0/7 Jan. 12, 1932. GRQSVENQR 1,840,315

ELECTRIC ELEVATOR SYSTEM Original Filed March 1, 1923 2 Sheets-Sheet 2- ATTO Y8 I Patented Jan. 12, 1932 UNITED STATES PATENT OFFICE GRAHAM B. GROSVENOB, OF CHICAGO, ILLINOIS, ASSIGNOR TO OTIS ELEVATOR COM- PANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY Original application filed The present application is a division of my copending application, Serial No. 622,149, filed March '1, 1923.

My invention relates to electric elevator systems and more particularly to systems in which the elevator is brought to rest at the landings by automatic means;

An elevator is rimarily a device'for raising or lowering 0 ]ects from one level to another and in order to get the maximum ser- -vice from a given equipment, it is necessary to have the elevators operate-at the highest possible average speed consistent with safety and comfort. This is an important consideration in buildings where floor space is valuable and traflic dense. In my copending application, Serial No. 563,094, I have described an elevator system'in which the elevator is automatically slowed .down and stopped at landings as desired by the operator, who initiates the slow-down and stop at some time prior-to reaching" the landing.

The operation of an elevator from one landing to another comprises acceleration and retardation, and in runs of distances great enough for maximum speed to be' atset.

tained, full speed running. In an ideal system, the time speed curves of acceleration and retardation must be of a definite form tocome from rest to. full speed and from full speed to rest in a minimum time. The retardation must be completed at or'just prior to reaching the landing.

One object of my invention is to provide an elevator system that will fulfill these conditions. In accomplishing this, I 'so design the system that the acceleration occurs'automatically after'the manual control has been speed, this full speed automatically continues .at the completion of acceleration, until the point is reached at which retardation is to 'be initiated.

In runs involving an interval of full ELECTRIC ELEVATOR SYSTEM Iarch 1, 1923, Serial No. 622,149. Divided and this application filed October 1, 1925, Serial No. 59,913. Renewed January 6, 1928.

always brought to a predetermined value depending on the load at or just prior to reach ing a point at a fixed distance from the landing. From this fixed point it then remains to bring the car to rest at the landing. In bringing the car to rest two operations are necessary. The power mustbe disconnected and a braking force must be applied. I

automatically disconnect the power at the fixed distance from the landing. The application of the braking force is madejust prior to disconnecting the power but preferably only strong enough to restrain the eflect of gravity upon disconnecting the power. When the power is disconnected the braking force is increased and the car brought to rest level with the landing without the necessity for correction by supplementary manual or automatic low speed operation. i

In the accomplishment of these-objects, I utilize many of the features of my copending application, Serial No. 563,094 and I have found that the elevator system described in from one floor to an adjacent floor, the start ing of the elevator being under control of the operator whereas the stopping is performed automatically-after being initiated by the operator, and i a Figure 2 is awiring diagram illustrating the circuits of the apparatus of Figure. 1.

Referringmore particularly to the drawings, an alternating current motor 1- is' shown as driving a direct current generator. 2 and an exciter 3. Power is supplied to motor 1 by mains 4, 5 and 6. It will be understood that the usual switches and starting devices may be used with motor 1. Generator 2 -has a separately excited field 7 which is sup lied' with current from 'exciter 3, which is a s unt V 5 ries field 12 for generator 2 is used between its armature and reversing switch 13. Elevator hoisting motor 14 is supplied with power by generator 2 through reversing switch 13 and is a separately excited motor.

ble number of cables 16 pass over it, one end of the cables being attached to the elevator 17 and the other to counterweight 18. A brake 19, having a slidably mounted core 24 and a plate 20 held against disc 21 by spring 22, serves to hold the elevator at rest. Disc 21 is secured to the shaft of sheave 15 and rotates with it. To release the brake, coil 23 is energized by current from exciter 3 so that core 24 is attracted and spring22 thereby compressed;

A governor 25, suitably located, is driven by cable 26 from the elevator and is equipped with contacts 27 and 28, the object of which is to stop the elevator in case of overspeed, as will be more fully described later. A car switch 29 is mounted in the elevator 17 and by it the operator controls the movements of the elevator. An emergency switch 30 is also 30 mounted in the elevator 17.

Elevator 17 is equip ed with a solenoid operated switch 31 whic when rendered operative by the operator, acts through the con trol circuits to slow down the elevator.

Switch 31 has a coil 176 and a magnetic core with an extension 33. Assuming coil 176 energized and the elevator going down, extension 33 will be attracted by the armature 34, which is mounted stationary in the hatchway, as soon as it comes op osite it. Contacts on switch 31 will open an the elevator will slow down,

When elevator 17 approaches the landing,

the extension 40 of the core of the solenoid V 45. operated switch 35, which is similar to switch 31, is attnacted'by the armature 36, thereby causing contacts on switch 35 to open, which provides a partial application of the brake preparatory to stopping.

The solenoid operated switch 37, when elevator 17 arrives at a floor landing, has its extension 39 opposite the stationary armature 38. The magnetic attraction causes extension 39 to move, which motion opens contacts on switch 37, thereby disconnecting elevator motor 14 from its power supply and fully applying the brake so that elevator 17 stops .level with the floor landing. V

To obtainthe most efficient transportation for floor to-floor travel, the elevator should have the maximum accelerationv and retardation allowable and should attain the maximum speed midway between two, adjacent floor landings This arrangement is advan- 55 tageous' in elevator transportation for build- Sheave 15 is driven by motor 14 and a suitaings having high floor heights and especially so where it is desirable that elevators stop at all landings.

Consider elevator 17 to be caused to travel from landing, 41 to landing 42. The operator, by moving handle 43 of car switch 29 in the proper direction, engages a series of contacts in the car switch 29 which complete cir cuits to directional and fast speed switches on the control panel, as will be described in detail in connection with Figure 2. The elevator immediately accelerates; the operator may now permit the car switch handle 43 to return to center. The fast speed and directional switches become self-holding upon being energized but are subject to being released automatically by the solenoid operated switches 31 and 37 when these switches attain a definite relation to the armatures 34 and- When elevator 17 is midway between landings 41 and 42, the elevator will be at full speed and switch 31 will be in the proximity of armature 34 which causes its-contacts to open. This will release the fast speed switch, thus causing the elevator to slow down at a definite rate. The length of armature 34 in the direction of elevator travel need be only sufiicientto insure the operation of switch31 and I have found four inches to be a suitable length. When elevator 17 is at the proper distance from landing 42 for the preliminary application of the brake, which takes place approximately at the time the elevator reaches its low speed, the solenoid operated switch 35 is caused to open its contacts, by coaction with armature 45. This causes a relay to open contacts 46 and 47, thereby inserting a suitable resistance 48 in series with the brake magnet coil 23. The brake is then applied partially by the'spring 22, the pressure of which will then be greater than the holding power of the brake magnet coil 23 by a predetermined amount. The length of armature 45 is chosen so that when elevator 17 is level with landing 42, extension 40 will be opposite its center.

The elevator will continue to approach the landing at low speed with the brake partially applied -until the extension 39 of solenoid operated switch 37 is magnetically attracted by armature 44 when switch 37 will open its contacts, thereby releasing the directional switches and interrupting the power to the 2 elevator motor and at the same time fully applying the brake to bring the car to a stop level with the landing. Armature 44 is of the proper length to permit of the elevator.

bein'g stopped by dynamic braking and by the electromechanical brake from low speed after disconnecting the elevator motor from In order that accurate stops may be made with variations of load in the elevator, it is important that the efiect of gravity due to such variations be compensated for by corresponding variations in the kinetic energy of the moving parts. This may be done by fix? ing the speed of the elevator, at the low speed from which stopping is done, in some direct proportion to the unbalanced load being lifted by the elevator motor. Means for accomplishing this are described in my copending application Serial No. 563,094.

It is to be noted that armature 34 serves to determine the point at which slow down will commence when the elevator approaches landing 42 from above. Armature 34 also determines the points of slow-down as the elevator approaches landing 41 from below.

Push-buttons 49 and 50 are provided on the car switch 29 for the purpose of operating the elevator in emergencies and emergency switch 30 is supplied to bring the car to rest immediately if desired.

' With electrical equipment where circuits may be energized intermittently, the resistance of these circuits will be subject to definite variation determined by the temperature change of the conductors through which the current flows. It is, therefore, desirable that certain elements, particularly the field windings of the motor generator set, exciter and elevator motor, should be wound with conductors which will have anegligibl temperature coefiicient in order that the resistances of these circuits will remain constant. In

this way speed characteristics of the equipment will be kept within definite bounds, which is an important consideration in the automatic slowing down and stopping of elevators. I

Figure2 is the wiring diagram for the system of Figure 1, the operation of -which is referred to in detaiL.

An A. G. motor 1 of a motor generator set driving an exciter 3, all of which are mechanically coupled, is connected to an A. C. source of supply through main line switch 51 and feeders 4, 5 and 6. Motor 1 should have asnearly constant speed as possible under different loads. I

The exc'ite'r 3,is shunt wound and self-excited, and sup lies a substantially constant voltage throng main switch 56, fuses 54 and 55 to feeders 52 and 53.

The generator 2 is of constant polarity and the strength ofzthe shunt field 7, when the elevator is at rest, is governed by the resistance of'its circuit which is from feeder 52 through line 57, resistance 58, line 59 to "shunt winding 7 of generator 2, line 60 to feeder 53 Upon closing of the emergency switch 30 onthe elevator, a circuit is obtained from feeder 52 through fuse 61, line 62, potential With the up switch coil 63, line 64, terminals G-G of traveling cable 66, line 68, emergency switch 30, line 69, terminals A-A of traveling cable 66, line 7 0 to lower hatchway, limit switch contacts 71 and 72, line 73 through hatchway, limit switch contacts 74 and 75, line 76, govcrnor switch contacts 28 and 27, lines 77 and 78, fuse 79 to feeder 53.

The potential switch, which is of the normally magnetically operated gravity returning type, is then energized and closes contacts 80 and 81, 82 and 83, 84 and 85, 86 and 87, at the. same time opening contacts 88 and 89.

Assume the elevator to be run in the up direction. In this case, carswitch-handle 43 is moved to the left until car switch contactor 90 touches car switch contact points 91, 92 and 93. The operation of this elevator being full automatic, the wiring is so arranged that-no action is obtained until car switch handle 43 is moved to the extreme running position at which time current may be distributed from the last contact finger engaged, which finger is termed the car switch feed.

-A circuit is then obtained from feeder 53 through fuse 79, line 78, contacts 86and 87,

lines 94 and 95, bottom contacts 96 and 97 of switches, two switches are utilized for each direction of travel, the magnet coils of each pair being connected in series, which results in both coi ls being energized at the same time.

The contacts controlled by the up direction switches are then closed or opened as follows :-Contacts 109 and 110, 111 and 112, 113 and'114, 115 and 116 are closed in the respective pairs as shown. Contacts 117 and 118 and 119 and 120 are opened in respective pairs.

circuits that function to start the elevator in motion are asfolldws :-Feeder 52, through fuse 61, ,line 62, contacts 83 and 82, line 108, contacts 116 and 115, lines 121, 122, 123, magnet coil 124 of the auxiliary brake switch, line direction switches closed, the

125, terminals H H of traveling cable 66, f

line 126, contacts 127 and 128, line 129, emer-.

gency switch 30, line 69, terminals A,-'A of traveling cable 66, line 70, contacts 71 and7 2, line 73, contacts 74 and 75, line 7 6, contacts auxiliary brakeswitch to close contacts 46 coil 23.

28 and 27, lines 77 and 78, fuse 79 to feeder 53.

Magnet coil 124 when energized, causes the and 47, which contacts short-circuit resistance 48, which is in series with brake magnet The brake magnet coil 23 is then suflicicntly energized to release the brake to permit the elevator motor to start. The circuit for the brake magnet is as follows From feeder 53, through line 130, contacts 81 and 80, line 131, brake magnet coil 23, line 132, contacts 47 and 46, line 133, contacts 109 and 110, line 134 to feeder 52.

The generator 2, having a definite field at all times the elevator is in service, is enabled to deliver current to the elevator armature at a predetermined low voltage immediately upon the closing of the directional switches.

The fieldof the elevator motor 14 has a constant value and is connected to the feeders as follows :Feeder 52, through line 136, adjusting resistance 137, line 138, shunt field coil 139, line 140 to feeder The elevator motor 14, having a constant field, will be enabled to start upon the armature of elevator motor 14 receiving current from the armature of generator 2.

The armature of elevator motor 14 receives power from generator armature as follows :F rom armature terminal 142 of generator 2 through line 143, series field 12, which is subject to variable strength as determined by adjustment of resistance 144 connected in parallel with series field 12, line 145, contacts 112 and 111, line 146, line 147, contacts 85 and 84, line 148, elevator motor armature terminal 149, through armature winding out through armature terminal 150, lines 151 and 152, contacts 114 and 113, lines 153 and 154, armature terminal 155 and through armature winding of generator 2.

The elevator motor has now started but as the car switch 29 must be moved to the extreme position in order to start the elevator motor in motion, the necessary circuits to obtain fast speed have also been made, resulting in the elevatoraccelerating to high speed as soon as the elevator has been started by means of the car switch.

The circuit for the fast speed switch is as follows :-From feeder 52, through fuse 61, line 62, contacts 83 and 82, line 108, contacts 116 and 115, lines 121, 122 and 156, through fast speed switch magnet coil 157, line 158, terminals I terminal slowdown contacts 160 and 161, line 162, contact 92 in the car switch, contactor 90, contact 93, line 98, terminals F F of traveling cable 66, 1ine,98',,contacts 97 and 96, lines 95 and 94, contacts 87 an'd86, line 78, fuse 79 to feeder 53. i

The fast speed switch magnet coil 157 causes contacts 163 and 164'to close, shortcircuiting resistance 58, which is 'i-n series I of traveling cable 66, line 159,

field winding of the generator 2, resulting in the building up of the magnetic field at a definite time rate determined by the character of the field circuit.

The building up of the magnetic field produces an increasing voltage in the armature windin of generator 2, which voltage is now imposed upon the armature of the elevator motor 14, causing the elevator to accelerate until the voltage has reached a maximumat which time the elevator will be at full speed.

After the control circuits as above described have been completed, it is not necessary to hold the car switch handle 43 at the running position,but it may be returned to its neutral position immediately. In such event, the elevator will continue to run until the automatic slowing down and stopping at the landing being approached come into action.

Whenthe car switch is returned to neutral position, the up direction and fast speed switches remain energized with sufficient current through the coils to keep these switches closed, but insufiicient current to enable the switches to pull in were they open.

To accomplish this, contact finger points 91, 92 and 93 in car switch 29 are tied together through suitable resistances, which resistances prevent the magnet switches on the control panel from pulling in if they are open. When the car switch has been moved to starting position, these resistances are short-circuited and the current in the magnet coils of the up direction and fast speed switches is increased to a value that is sufficient to close the switches controlled.

Car switch finger point 93 is tied to contact finger point 91 through lines 98 and 165, contacts 166 and 167, line 168, resistance 169 and line 99. I

Car switch finger point 93 is tied to contact finger point 92 through lines 98, 165 and 170, contacts 171 and 172, line 173, resistance 174 and line 175.

The coil 176 of the magnetically. operated slow-down switch on the car isnenergized from feeder 53, fuse'79, lines 78 and 77, contacts 27 and 28 on the overspeed governor, line 76, contacts 75 and 74 on the up overtravel limit, line 73, contact-s 72 and 71 on the down overtravel limit, line 7 0, terminals A A of traveling cable 66, line 69, emergency switch 30, line 129, automatic slowdown coil 176, line 177, terminals B-B of traveling cable 66, line 121, contacts 115 and 116, line 108, contacts 82 and 83, line 62, fuse 61 to feeder 52.. L

When the elevator is approximately midway between two adjacent floors, aprojection of the core of magnet coil O17 6-wil1 be opp0- site the stationary armature 34 (see Figure 1 for arrangement). The motion of the core value of the series resistance 58' has been.

loads than that obtained when lifting will open contacts 171 and 172 which are included in the self-holdin circuit for the magnet 157 ofthe fast speed switch on the control panel. Contacts 163 and 164 on the fast speed switch will open inserting resistance 58 in series with the field winding 7 of the generator. The field of generator 2 will dischar e through resistance 11 which is across win ing 7 The time rate of field discharge will be determined by the resistance 11 connected across the terminals of field 7 and may be increased or decreased, as desired, by changing the value of resistance 11. As the generator field discharges its energy, the voltage of the generator. will decrease until the minimum voltage determined by the reached and the elevator will then run at low speed.

The series field 12 assists in decreasing the total magnetic field, due to the regenerative action 0 the elevator motor when slowing down. The current in the series field is reversed during slow-down period and the magnetic fiux due to it will be in opposition to that of the separately excited field. This action therefore supplements the discharge resistance across the field winding 7.

At slow speed the series field acts to compensate for load and by properly proportioning the strength of the series'fie'ld, a lower speed may be obtained when lowering The fast speed switch, when its 0011 is deenergized, also closes contacts 17 8 and 179, which provides the following circuit'z-From feeder 52 through fuse 61, line 62, contacts 83 and 82, line 108, contacts 116 and 115, lines 121,122 and 156, contacts 178 and 179, line 180, terminals J-J of traveling cable 66, line 181, automatic brake and stopping switch coils 182 and 737 in parallel, line.129, emergency switch 30, line 69,'terminals A-A of traveling cable 66, line 70, contacts 71 and 72, line-73, contacts 74 and 75, line 76, contacts 28 and 27, lines 77 and 78, fuse 79, line 53.

' Upon'approaching the floor, the core of magnet 182 is caused to move when it comes opposite armature 36. This opens contacts 128 and 127 and deenergizes magnet 124, causing contacts 46 and 47 'to open thereby inserting resistance 48 in series with brake magnet 23. This weakens brake magnet 23 which can no longer counteract the action,of the brake sprihgs entirely, resulting in partial applicationbf the brake shoes.

The elevator continues to approach the floor landing until the magnet core of magnet 737 comes opposite stationary armature 38 at whichtime contacts 166 and 167 will open and the up direction switch magnets 105 and 106 will be deenergizedi The .up: direction switch in droppin out opens contacts-109 and 110, 111 and 112, 113 and .114 and115 and 116. The opening of these contacts permits loads.

full application of the brake, interrupts power supply to the elevator armature as well as current to the automatic switches on the car, and to the fast speed switch on the control panel. I

The'elevator will now come to rest from low speed approximately level with the landing,through the'action of the electro-mechanical brake and the dynamic braking ac-- tion of resistance 185, the circuit of which is as follows :--From elevator armature terminal 149 through line 148, contacts 84and'85, lines 147 and 183, contacts 118 and 117, line 184,

dynamic resistance 185, line 186, contacts 187' and 188, lines-189 and 151, armature terminal 150 and elevator motor armature winding.

I The potential switch which is controlle by the .magnet 63 maybe opened by various safety means such as the emergency switch 30 in the car, overtravel limit switch contacts 71 and 72 or 74 and 75 in the hatch, overspeed governor contacts 27 and 28 and other usual safety devices. Upon deenergizing the poten-' tial switch magnet coil 63, contacts and 81,

82 and 83, 84 and 85 and 86 and 87 are opened invention, under normal operation, the starting of-the elevator is under control of the operator whereas its acceleration and stopping are automatically controlled; 'the operator 1 while contacts 88 and 89 are closed. The contacts that open interrupt power supply to the merely selecting at some time previous to'the elevator reaching it, the floor at which he desires to stop and then manipulating the car'switch tothro'w the automatic stopping means into operative condition. Since the elevator reaches full speed in making one floor runs, the stopping is accomplished by the same means whether the-elevator is caused to travel one floor or vtwo or more.floors.be-

fore stopping. I

I also wish to point out that I provide means for causing the preliminary application of a braking force before the power supply to the elevator motor is interrupted',-this braking force being of a predetermined strength and preventing the momentary acceleration of the car by gravity between cutting off the power and applying the final brakingforce. Furthermore, as a part of the braking operation has already occurred,

the application of the final braking force is able to accomplish its purpose that ,much more quickly. I believe this principle to be broadly new for the purpose here employed;

whether these forces are developed in one brake or a plurality of brakes, and the illustration of the principle as applied to the use of a single brake is intended to illustrate the broad principle as stated.

I claim 1. An electric elevator system comprising in combination; a plurality of landings including at least one intermediate landing; an elevator car; a hoisting motor for said car; electromechanical braking means for said motor; and means for causing the motor to slow down and stop the car at any selected one of said landings, said last included means comprising means for automatically discontinuing the power supply to said hoisting motor on approaching the landing selected, means for automatically causing a partial braking in predetermined amount before said discontinuation of the power supply, and means for applying full braking on discontinuation of the power supply.

2. An elevator system comprising in combination, a plurality of landings including at least one intermediate landing, an elevator car, a hoisting motor for said car, electrovsuch landing less than said predetermined mechanical braking means for said motor, and means for causing the motor to slow down and stop the car at any selected one of .said landings, said last included means comprising means carried by the car and automatically operated upon the arrival of the car at a predetermined distance from the landing selected to cause a partial application ofsaid braking means and means also carried by the car and automatically operated upon the arrival of the car at a less distance than said predetermined distance from such landing to cause full application of said braking means.

3. An elevator system comprising in combination, a plurality of landings including at least one intermediate landing, an elevator car, a hoisting motor for said car electromechanical braking .means for said motor, andmeans "for causing the motor to slow down and stop the car at anyselected one of said landings, said last included means comprising a switch carried by the car and operated automatically upon the arrival of the car at a predetermined distance from the landing selected to cause a partial application of said braking means and a switch also carried by the car 'and operated automatically upon the arrival of the car at a distance from distance to cause full application of said braking means.

4. An elevator system com bination, a plurality'of lan ings' including at least one intermediate landing, an elevator car, a hoisting motor for said car, electromechanical 1 braking means for said motor, and means for causing the 'motor to slow down -and stop the car at any selected one rising in comof said landings, said last included means operation ofsaid switch as the car arrives at.

a predetermined distance from the landing selected. V

v 5. An elevator system comprisin in combination, a plurality of landing-s inc uding at least one intermediate landing, an elevator car, ahoisting motor for said car, electromechanical braking means for said motor, and means for causing'the motor to slow down and stop the car at any selected one of said landings, said last included means comprising means for automatically causing the braking means to be partially applied upon the arrival of the car at a predetermined distance from the landing selected and means for automatically causing the braking means to be fully applied and the supply of power to said hoisting motor to be discontinued upon the movement of the car a certain distance beyond the point at which the braking means are caused to be partially applied.

6. An elevator system comprising in combination, a plurality of landings including at least one intermediate landing, an elevator car, a hoisting motor for said car, electromechanical braking means for said motor, and means for causing the motor to slow down and stop the car at any selected one of said landings said last included means comprising mcans rendered operative by the operator in selecting a landing for causing the braking means to be partially applied upon the arrival of the car at a predetermined distanceufrom the landing selected and means for thereafter causing the brakin force exerted by said braking means to be increased and the supply of motor to be discontinued.

7. An elevator system comprising in combination, a plurality of landings including at least one intermediatelanding, an elevator power to said hoistingcar, a hoisting motor for said car, electromechanical braking means for said motor, and means for causing the motor to slow down and stop the car at each one of said landings, said last included means comprising a control in the hatchway for each landing for causing thepartial application of said braking meansupon the arrival of the car at a predetermined distance from the landing for which the control is provided and an additional control in the hatchway for each landing for causing full application of the braking means, after the partial application thereof, upon the arrival of the car at a less distance from the landing for which the additional control is provided.

8. An elevator system comprising in combination, a pluralityof landings including at least one intermediate landin an elevator car, a hoisting motor for sai car, electromechanical braking means for said "motor, andmeans for'causing the motor to slow down and stop the car at each one of said landings, said last included means comprising a control in the hatchway for each landing and means carried by the car and common to all of the landings for cooperating with each of said controls to cause the partial application of said braking means upon the arrival of the car at a predetermined distance from the landing for which the control is provided. 7

9. An elevator system comprisin in combination, a plurality of landings inc uding at least one intermediate landing, an elevator car, a hoisting motor for said car, electromechanical braking means for said motor, and means for causing the motor to slow down and stop the car at each one of said landings, said last included means comprising a magnet carried by the elevator car and having a plurality-of armatures, one for each of said'landings, and a switch also carried by the elevator car and actuatable by the coaction of said magnet and each armature to cause a partial application of the braking means upon the arrivalof the car at a pre determined distance from the landing for which the armature is provided.

10. An elevator system comprising in combination, a plurality of landings including at least one intermediate landing, an elevator car, a hoisting motor for said car, electromechanical braking means for said motor, and means for causing the motor to slow down and stop the car at each one of said landings, said last included means comprising an electromagnet carried by the elevator car and having a plurality of armatures, one for each of said landings, another electromagnet carried by the car and having a plurality ofarmatures, one for each ofsaidlandings, aswitch also carried by the car and actuatable by the coaction of the first named electromagnet and each of itsiarmatures to cause a partialapplication of the braking means upon the arrival of the car at a predetermined distance from the landing for which the armature is provided, and another switch also denied by the car and actuatable by the coaction of the second named magnet and each of its armatures to cause full application of the braking means, after the partial application thereof, upon the arrival of the car at another predetermined distance from the landing for which the armature is provided, such second named distance being less than the first named distance.

GRAHAM B. GRosvEN oR; 

